Conventionally, in a flat knitting machine, a knitted fabric is produced in such a manner that a carriage travels back and forth along the longitudinal direction of the front and the back needle beds opposing each other at a needle bed gap, knitting needles are moved forward to and backward from the needle bed gap by a knitting lock mounted on the carriage, and yarn is supplied to the knitting needles from a yarn carrier brought by the carriage. By measuring the length of the yarn absorbed into the knitted fabric during knitting and by correcting the stitch density positions of stitch cams pulling down the knitting needles on a knitting lock, it is possible to control the length of the yarn so that the yarn in a knitting stitch loop has a predetermined length (refer to Japanese Patent No. 3085638 and Japanese Unexamined Patent Publication JP-A-8-120548 (1996), for example). Such yarn length control can be performed also with a yarn feeding apparatus for supplying yarn (see JP-A-2002-227064, for example).
Conventionally, the length of a yarn is controlled in different manners between a plain knitted texture knitted using adjacent knitting needles in the same needle bed and a rib stitch texture knitted using knitting needles alternately in needle beds opposing each other. This is because in the case of a rib texture, it is necessary to include yarn crossing the needle bed gap between the needle beds. Yarn used for knitting is selected among those from a plurality of yarn carriers and supplied. For each of the yarn carriers, yarn itself is different, or a route on which yarn is supplied is different, and thus the length of the yarn is controlled based on correction data that is different for each of the yarn carriers. Furthermore, in a carriage, at least with respect to each of the front and the back needle beds, a stitch cam for performing knitting in a travel to one side in the longitudinal direction and a stitch cam for performing knitting in a travel to the other side in the longitudinal direction are provided. Thus, each of the stitch density positions of the four stitch cams in total is corrected and adjusted so that the constant length of yarn in a knitting stitch loop can be obtained when performing knitting using any stitch cam. In some cases, a plurality of sets of knitting locks are mounted on the carriage so that a plurality of knitting operations can be performed in one travel in the longitudinal direction of the needle beds. In such cases, the stitch density positions of the four stitch cams are corrected for each of the sets of the knitting locks.
Knitted articles that are subjected to be produced in a flat knitting machine are garments such as sweaters and have a tubular form covering the body three-dimensionally. A method has been developed by which in a flat knitting machine provided with the front and the back needle beds, a knitted article that will have a tubular form in the completed state is produced by knitting main portions of the knitted fabric such as a front body and a back body separately from each other so that the portions have various textures and patterns. However, a final tubular knitted article cannot be obtained unless the partial knitted fabrics knitted separately are joined by sewing. A tubular knitted article can be produced also in one piece, for example, when while knitting a front knitted fabric of the tubular knitted article at the front needle bed and a back knitted fabric of the tubular knitted article at the back needle bed respectively, the knitted fabrics are joined together on both of the end sides in the knitting width and the knitting yarns are led to go around. In this case, only front stitches are formed on the knitted fabric texture. A knitted fabric texture that is produced using the front and the back needle beds and that is substantially similar to a texture obtained by producing each of the knitted fabric portions separately can be knitted by a method by which a front portion and a back portion of the tubular knitted fabric are allocated to the knitting needles in each of the needle beds alternately (see JP-B2-3-75656 (1991), for example).
FIG. 8 shows an example in which in a flat knitting machine provided with the front and the back needle beds, knitting needles are alternately allocated to a front portion and a back portion of a tubular knitted fabric. Each of the needle beds is provided with a plurality of knitting needles arranged with an equal pitch along the longitudinal direction. The knitting needles are sequentially numbered from one side in the longitudinal direction and divided into needles with odd numbers and needles with even numbers, and one side shown by capital letters is allocated to knitting of the front portion of the knitted fabric and the other side shown by lower-case letters is allocated to the back portion. With this allocation of the knitting needles, when each of the front knitted fabric shown by the solid line and the back knitted fabric shown by the broken line is knitted by drawn off stitching, a knitting needle on the back needle bed can be used for knitting the front portion at any position such as the position C. Also with respect to the back portion, any knitting needle on the front needle bed can be used in a similar manner.
In this manner, although the front and the back portions are knitted in one piece in the flat knitting machine provided with the needle beds on which the knitting needles are arranged with a pitch of AaBbCc . . . , each of the portions is equivalent to a portion knitted separately in a flat knitting machine provided with needle beds on which the knitting needles are arranged in pitches of ABC . . . and abc . . . . In a flat knitting machine, an arrangement pitch of knitting needles is typically expressed in gauge, which is the number of needles in 25.4 mm (1 inch). Thus, in a method such as shown in FIG. 8, using a flat knitting machine with a gauge of 5, it is possible to knit, in one piece, a tubular knitted fabric that is similar to a fabric obtained when each of the portions is knitted in a flat knitting machine with a gauge of about 2.5 to 3.
Referring to FIG. 9, FIG. 9(a) shows yarn pulled down by the knitting needles in drawn off stitching in which the knitting needles in every second line are used, and FIG. 9(b) shows yarn pulled down by the knitting needles with a pitch having the equivalent effect to that realized by the drawn off stitching in FIG. 9(a), in whole needle knitting in which all of the knitting needles are used. More specifically, in knitting as shown in FIG. 9(a), knitting is performed using the needle bed as a needle bed with a gauge that is different from the gauge expected when whole needle knitting is performed in the needle bed. Herein, in drawn off stitching using every second needles as shown in FIG. 9(a), substantially, knit and miss are performed alternately. In a knit knitting operation, yarn is pulled down between sinkers shown by the dashed dotted lines on both sides of each of the knitting needles. The width between the sinkers arranged on both sides of each of the knitting needles in each of the needle beds in FIG. 9(a) is smaller than the width between the sinkers arranged on both sides of each of the knitting needles in the needle bed with a different gauge in which the pitch is double, as shown in FIG. 9(b), due to the existence of the adjacent knitting needles. For example, in a case in which knit knitting is performed with the knitting needle B, adjacent knitting needles thereof are not the knitting needles A and C, but the knitting needles a and b, so that the width between the sinkers is narrow. Thus, when the same amount of the knitting needles pulled down is set, the length of the yarn in knitting stitch loops is short in the case of drawn off stitching. The difference in the lengths of the yarns in the knitting stitch loops results in the difference in the feelings of the knitted articles. In drawn off stitching, in order to realize the knitting stitch loops that are equivalent to the loops obtained in knitting with a different gauge having the equivalent effect, a method is conceivable by which the amount of the knitting needles pulled down by the stitch cams on the knitting lock is increased, but it is difficult to pull down sufficiently due to restrictions regarding the strength of the knitting yarn and the shape of the cams.
FIG. 10 shows the manner of a drop loop, in drawn off stitching using every second needles, which can realize a yarn length that is similar to the length of a knitting stitch loop obtained by whole needle knitting in a flat knitting machine having a different gauge as shown in FIG. 9(b). For example, when knitting stitch loops of a back knitted fabric are held by the knitting needles abc . . . on the front needle bed, first, the knitting stitch loops are transferred to the back needle bed side so as not to be held by the knitting needles abc . . . , a front knitted fabric is produced by the knitting needles ABC . . . , and the knitting yarn is pulled down by the knitting needles abc . . . on the front needle bed, as shown in FIG. 10(a). By letting the knitting needles abc . . . perform a knitting operation again, the knitting yarn pulled down by the knitting needles abc . . . is shook off from the knitting needles abc . . . and absorbed into knitting stitch loops formed by the adjacent knitting needles ABC . . . , as shown in FIG. 10(b). With this drop knitting in which a hung stitch is formed and then the stitch is shook off, the length of yarn in a knitting stitch loop can be made long more easily than repeating knit and miss alternately.
By performing knitting in which a drop loop is used as shown in FIG. 10, in a case in which a tubular knitted fabric is produced by drawn off stitching, the feeling of the produced knitted fabric can be made equivalent or similar to the feeling of a knitted fabric produced with a different gauge. However, by the amount of the knitting yarn absorbed after shaking of the hung stitch, the formed drop loop has a longer length than a knitting stitch loop formed by a simple knit knitting, and thus it is impossible to perform knitting so that the length of the yarn is uniform with a sufficient precision in conventional yarn length control intended for a stockinette texture and a rib texture. Furthermore, when adjacent knitting needles are separated between the front and the back needle beds in drawn off stitching, the knitting yarn is necessary for an extra portion crossing the needle bed gap from the hung stitch to a knitting needle in the other needle bed. This extra yarn is absorbed into the drop loop after shaking off the hung stitch, and thus in knitting under the same condition, the length of the yarn in the drop loop with a crossing portion is longer than that without a crossing portion.